(a) Field of the Invention
The invention described herein relates to novel compounds classified in the field of organic chemistry as phthalides, useful as color-forming substances, particularly in the art of transfer imaging and pressure-sensitive and thermal responsive carbonless duplicating; to transfer imaging systems containing said compounds; to pressure-sensitive and thermal responsive carbonless duplicating systems containing said compounds; to novel 2-indolylcarbonylbenzoic acids, useful as intermediates to said phthalides; to novel indoles, useful as intermediates to said phthalides and to said benzoic acids; and to processes for preparing said phthalides, benzoic acids and indoles.
(b) Information Disclosure Statement
Several classes of organic compounds of widely diverse structural types are known to be useful as colorless precursors for transfer imaging systems. Among the more important classes, there may be named leuco-type dyestuffs such as: phthalides, for example, crystal violet lactone, Malachite green lactone; fluoran, for example, 3-dialkylamino-7-dialkylaminofluoran, 3-dimethylamino-6-methoxyfluoran; phenothiazines, for example, benzoyl leuco methylene blue; Rhodamines, for example, Rhodamine-B-anilinolactone; and spiro-dinaphthopyrans, for example, 3-methyl-spiro-dinaphthopyran. The classes of organic compounds listed above also generally find utility in pressure-sensitive and thermal responsive carbonless duplicating systems.
Typical of the transfer imaging systems is the system described in U.S. Pat. No. 4,399,209 which issued Aug. 16, 1983. In this patent a transfer imaging system is disclosed wherein images are formed by image-wise exposing a layer comprising a chromogenic material and pressure rupturable containing as an internal phase, a photosensitive composition. In this system the chromogenic material is encapsulated with the photosensitive compound. Upon exposure to filtered U.V. or blue light in the wavelength range of 380 to 480 nanometer a certain portion of the capsules will harden. The capsules in which the internal phase has remained liquid are ruptured and the chromogenic material is image-wise transferred to a developer or copy sheet where the chromogenic material reacts with a developer to form an image.
Typical of the many commercially accepted pressure-sensitive and thermal-responsive carbonless copy systems are those described in U.S. Pat. Nos. 2,712,507; 2,800,457; 3,041,289; and 4,000,087, which issued July 5, 1955; July 23, 1957; June 26, 1962; and Dec. 28, 1976, respectively.
Many of the color formers in the prior art suffer one or more disadvantages such as low tinctorial strength, low resistance to sublimation, low susceptibility to copiability of the color-developed images in standard office copying machines, for example, a xerographic type of copier, poor image stability in the pressence of light, i.e., the product image fades losing intensity or changes to a less acceptable color, and low solubility in common organic solvents. The latter disadvantage requires the use of specialized and expensive solvents in order to obtain microencapsulated solutions of sufficient concentration for use in pressure-sensitive copying systems and transfer imaging systems.
The following items to date appear to constitute the most relevant prior art with regard to the instant invention.
U.S. Pat. No. 4,062,866, issued Dec. 13, 1977 discloses phthalides having the structural formula. ##STR1## wherein R.sub.1 and R.sub.2 independently of the other, represent hydrogen, alkyl with 1 to 12 carbon atoms, alkoxyalkyl with 2-8 carbon atoms, cycloalkyl with 5 or 6 carbon atoms, benzyl or phenyl, X represents alkyl with 1 to 12 carbon atoms, alkoxy with 1 to 12 carbon atoms or acyloxy with 2 to 12 carbon atoms, Y represents alkyl with 2 to 12 carbon atoms, alkoxy with 3 to 12 carbon atoms or acyloxy with 2 to 12 carbon atoms, Z represents hydrogen, alkyl having 1 to 12 carbon atoms or phenyl, U represents alkyl having 3 to 12 carbon atoms, benzyl or cyanoethyl, or may also represent W when R.sub.1 and R.sub.2 both are benzyl, W represents hydrogen, methyl or ethyl and n is 1 or 2, the benzene rings A and B may be substituted by alkyl with 1 to 6 carbon atoms and the benzene ring B may also be substituted by nitro or halogen. The phthalides are particularly useful as color formers which give intense blue colors when they are contacted with an electron-accepting co-reactant such as silton clay or a phenolic resin.
British Patent No. 1,422,096, which was published Jan. 21, 1976 discloses phthalides having the structural formula ##STR2## wherein A together with the carbon atoms to which it is attached represents an unsubstituted benzene ring; a naphthalene or a heterocyclic ring; R.sub.2 and R.sub.2 each independently represents hydrogen, C.sub.1-4 alkyl or aryl; R.sub.3 and R.sub.3 independently represent hydrogen, C.sub.1-4 alkyl or C.sub.1-4 alkoxy; and R.sub.1 and R.sub.1 each independently represents hydrogen, aralkyl, unsubstituted or substituted (excluding aryl substituents) C.sub.1-18 alkyl or unsubstituted or substituted C.sub.3-18 alkenyl. The phthalides are particularly useful as color formers in heat-sensitive recording material.
U.S. Pat. No. 3,491,116, issued Jan. 20, 1970, discloses phthalides having the structural formula ##STR3## wherein R.sub.1 and R.sub.2 comprise alkyl radicals having from one to five carbon atoms, aryl radicals, and hydrogen; and R.sub.3 and R.sub.4 comprise alkyl radicals having from one to five carbon atoms and hydrogen. The phthalides are particularly useful as color formers in pressure-sensitive recording material which contain Lewis acid molecules as color developers.
U.S. Pat. No. 4,399,209, issued Aug. 16, 1983, discloses a transfer imaging system in which images are formed by image-wise reaction of one or more chromogenic materials and a developer, said system comprising: an imaging sheet comprising a first substrate; a chromogenic material; a radiation curable composition which undergoes an increase in viscosity upon exposure to actinic radiation; a coating on one surface of said first substrate comprising said chromogenic material and said radiation curable composition; said radiation curable composition being encapsulated in rupturable capsules as an internal phase; and a developer sheet comprising a second substrate and a developer material capable of reacting with said chromogenic material to form an image on one surface of said second substrate; wherein images are formed by image-wise exposing said coating to actinic radiation, and rupturing capsules in the image areas with said coating in facial contact with said developer sheet such that said internal phase is image-wise released from said ruptured capsules and there is imagewise transfer of said chromogenic material to said developer sheet and a patterned image-forming reaction occurs between said chromogenic material and said developer material.